What does << means in javascript

Question

I am looking at some code in javascript

var numCombos = 1<<numActive;

numActive = 8 returns numCombos = 256

what does << means?

score 4 · Answer 1 · edited May 23 '17 at 12:13

It's the bitwise left operator. In a << b, it shifts a in binary representation b (< 32) bits to the left, shifting in zeros from the right.

Some examples:

a = 1       // 00000001 in binary
b = a << 1  // equals to 2, 00000010 in binary
c = a << 2  // equals to 4, 00000100 in binary

document.write('a << 1 = ' + b + '<br />'
               + 'a << 2 = ' + c);

This operator is kind of standard, and a little search should lead you to a lot of already existing topics on StackOverflow like this one: << operator in C++? or even this one: What are bitwise shift (bit-shift) operators and how do they work?

score 3 · Accepted Answer · answered Mar 12 '14 at 06:38

3

It means bitwise left shift. Same as it means in most other programming languages.

Some console test:

>a = 2
2
>a << 1 
4
>a << 3
16

answered Mar 12 '14 at 06:38

DhruvPathak

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1

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators – Michiel van Vaardegem Mar 12 '14 at 06:39
3

@edelweiss if you had googled then it would have been much more faster :P – Raghu Mar 12 '14 at 06:41

What does << means in javascript

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